184* Scientific Intelligence^ 
Carbonate of strontian, 
Spermaceti crystallised, 
37 
40 
Sulphate of magnesia and soda, 
46 
49 
A new mineral, 
56 
6 
Epidote, « , _ 
84 
19 
7. Crystals with one Axis of Double Refraction , — The fol- 
lowing crystals have been found by Dr Brewster to have one 
axis of double refraction : 
Positive Class, Negative Class. 
Oxide of tin. Molybdate of lead. 
Apophyllite from Fossa, Carbonate of iron and lime. 
Other crystals have been found to have one axis from the tints, 
but as the single system of rings was not seen, they have not 
been inserted here. 
8. Rfractive power of Hyposulphite of Soda and Silver . — * 
Mr Herschel has found the indices of its two refractions to be 
1.735 and 1.785, 
9. Nitrite of Lead . — Mr Herschel has found the index of 
the ordinary refraction of this salt to be 2.322. He found also 
that it had two resultant axes. We suspect, however, that it 
may have been another salt, or may have contained impurities ; 
as the nitrite of lead which we examined, and which was made 
by an able chemist, had no double refraction, and no polarising 
structure. 
10. Illuminating power of Gases . — Mr Brande has recently 
found that the illuminating powers of olefiant^ oil and coal gases, 
are as the numbers 3, 2, and 1, and that their heating powers 
are nearly in the same ratio. 
MAGNETISM. 
11. Captain Scoreshy on the anomaly in the Variation of the 
Needle . — A very interesting paper on this subject, by our able 
correspondent Captain Scoresby, has been published in the 
Phil. Trans, for 1819, Part I. The following are some of the 
results of his observations : 
1. All the iron on board a ship has a tendency to become 
magnetical, the upper ends of the opposite bars being S. and 
the lower N. poles in the Northern Hemisphere, and vice versa. 
